LOS ANGELES—When the Mayme A. Clayton Library & Museum of African American History & Culture is finished it will rival New York's Schomburg Center for Research in Black Culture in size and significance.

Clayton's son, Avery Clayton, is still cataloging the hundreds of thousands of things his mom collected before she died in 2006 at the age of 83.

But he is also getting ready for the museum's first major exhibition. It's a joint project with the Huntington Library, Art Collections, and Botanical Gardens in San Marino and will be held Oct. 24 to Jan. 4.